1. Field of the Invention
The present invention relates to a disc brake assembly for wheeled vehicles, and more particularly to the disc brake assembly which includes a brake pad having a pair of ear portions which are projected outwardly at a center portion or an outer side from the center portion of both ends in the rotational direction of the disc rotor and its backing plate, respectively, and which are fitted into a pair of groove portions formed in an arm portion of a mounting member which is fixed to a part of a vehicle body, and slidably supported on each arm portion toward to the axial direction of the disc rotor. Further, the present invention relates to a disc brake assembly which receives a friction force due to operation of the brake pad by the disc rotor under the disc brake assembly operating condition with a torque resisting surface of the arm portions of the mounting member contacting with the end surface of the backing plate in the rotational direction of the disc motor.
2. Description of the Related Art
A conventional disc brake assembly of this kind is disclosed, for example, in Japanese Utility Model application laid-open publication No. 62-96134 published on June 19, 1987. This conventional disc brake assembly includes a pair of brake pads having backing plates whose both end surfaces in the rotational direction of the disc rotor at a substantially center portion (press center) of each brake pad and the mounting member having torque resisting surfaces which are opposite to the both end surfaces of the backing plate in the rotational direction of the disc rotor in parallel. In this conventional disc brake assembly, the friction force transmitted to the brake pad toward the tangent direction is vertically transmitted to the torque resisting surface when the disc brake assembly is operated and the brake pad does not receive a force in the diameter direction of the disc rotor, therefore each brake pad is in an unstable condition when the disc brake assembly is operated.
An analysis of the relationship between movement of each brake pad and the generation of an acceptable squeak noise of the disc brake by various experiments. As a result, it was confirmed that since each brake pad is unstable in the diameter direction of the disc rotor, as shown by FIG. 9, if a friction force F transmitted to each brake pad (the position of the press center) changes in the diameter direction of the disc rotor due to a concavity or convexity of the frictional surface of the each brake pad, a swing of the disc rotor, a bend of the caliper member (the bridge portion of the caliper member bends so as to separate the reaction portion from the cylinder portion) and so on, each brake pad 2 is moved with respect to the torque receiving surface 1a of the mounting member 1 as shown by an imaginary line in FIG. 9. Further, if an uncomfortable squeak noise of the disc brake assembly is generated when the disc brake assembly is operated, each brake pad is subjected to movements as mentioned above, and in case of the generation of an acceptable squeak noise of the disc brake assembly the brake pads have very little movement.
For preventing the uncomfortable squeak noise of the disc brake assembly, as discussed above, the various noise preventing means, for example a means for equalizing a distribution of the dynamic pressure of each brake pad (a means for regulating the press center of each brake pad, for example, positioning a shim plate between the backing plate of each brake pad or offsetting the press center of each brake pad) and so on have been proposed. However, since these measures for preventing noise relate to the shape of the backing plate of each brake pad and each arm portion of the mounting member supporting each brake pad, it is impossible to perfectly prevent all of the movement of each brake pad as shown by FIG. 9 and it has been unable to prevent the squeak noise of the disc brake assembly.